The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
It is often necessary to use equipment powered by internal combustion engines within confined environments such as internally within buildings, trenches and other closed working environments. In such circumstances, exhaust gases from the internal combustion engines are discharged into the closed environment and can accumulate to an extent where the exhaust gases often create hazardous working conditions. It is therefore desirable to remove the exhaust gases from the closed environment.
There have been several proposals for removal of exhaust gases emitted from internal combustion engines operating within closed environments. One such proposal is disclosed in AU2004284110 which is directed to an extraction apparatus operable to capture exhaust gas emitted from the internal combustion engine and mix the exhaust gas with air to both dilute the exhaust gas and to also have a cooling effect on the exhaust gas. Water is also injected into the incoming air to have a further cooling effect on the exhaust gas. The resultant mixture of exhaust gas, incoming air and injected water is then extracted, typically by way of a suction line, and conveyed to a remote location away from the closed environment.
While the arrangement disclosed in AU2004284110 has proved to be a commercial success, certain improvements can be contemplated.
In the arrangement disclosed in AU2004284110, there is provided an axial flow passage defining an air flow path from an air inlet to an outlet which is connected to the suction line. The exhaust gas from the engine is delivered into the flow path for mixing with the air flow by way of an exhaust gas inlet having a tubular discharge section opening onto the flow path. The discharge section is centrally located within the flow passage and extends along the flow passage towards the outlet. The centrally located discharge section can constitute an impediment to flow along the flow path and so restrict the volume of exhaust gas that is capable of being handled. The restriction can possibly also adversely affect engine performance, as it can create a lower pressure zone at the location at which the centrally located discharge section opens onto the flow path. The lower pressure zone can lead to creation of a negative pressure at the engine exhaust, thereby adversely affecting engine performance. This provides an area where improvement may be contemplated.
In certain instances, it is possible that there might not be adequate mixing between the exhaust gas and the air. In particular, there might, for example, be inadequate mixing between the exhaust gas and the air, as well as any water injected into the fluid flow, within the extraction apparatus prior to the fluid flow discharging from the outlet to which the suction line is connected. This inadequate mixing may result in the formation of hot spots in the suction line, particularly in the region immediately downstream of the extraction apparatus, leaving the suction line vulnerable to heat damage, perhaps even to the extent of melting in parts. This provides an area where improvement may be contemplated.
Further, while the arrangement disclosed in AU2004284110 provides some cooling of the exhaust gas, an improvement to the extent of available cooling may also be contemplated.
Still further, while the arrangement disclosed in AU2004284110 may afford some cooling of the exterior part of the extraction apparatus exposed to contact with a user while the extraction apparatus is in operation, an improvement to the extent of available cooling may also be contemplated.
It is against this background, and the problems and difficulties associated therewith, that the present invention has been developed. The present invention need not necessarily address any or all of these areas where improvement has been contemplated; rather, development of the invention has been motivated by recognition of these areas for potential improvement.
At the very least, the present invention provides a useful choice to that available by way of the arrangement disclosed in AU2004284110.